The present invention is directed to a defibrillation device, and more particularly to a personal wearable pacer/cardioverter/defibrillator which monitors a patient""s condition, detects shockable or paceable arrhythmias, determines consciousness, and, in the case that the patient is determined to be unconscious, administers therapy to the patient.
Cardiac arrhythmias, such as ventricular fibrillation and ventricular tachycardia, are electrical malfunctions of the heart, in which regular electrical impulses in the heart are replaced by irregular, rapid impulses. These irregular, rapid impulses can cause the heart to stop normal contractions, thereby interrupting blood flow therethrough. Such an interruption in blood flow can cause organ damage or even death.
Normal heart contractions, and thus normal blood flow, can be restored to a patient through application of electric shock. This procedure, which is called defibrillation, has proven highly effective at treating patients with cardiac arrhythmias, provided that it is administered within minutes of the arrhythmia. In the past, this was not always possible, since defibrillation units were large, and thus not easy to move, and could only be operated by an experienced clinician.
In response to the foregoing drawbacks of defibrillation units, implantable defibrillators were developed. Such defibrillators, however, also have several drawbacks. Specifically, use of a such a defibrillator requires surgery, thereby making their use inconvenient and even undesirable under certain circumstances. Moreover, implantable defibrillators are also costly, both in terms of the device itself and in terms of the cost of the surgery and subsequent treatments.
To address the foregoing drawbacks of implantable defibrillators, portable automatic external defibrillators (hereinafter xe2x80x9cAEDsxe2x80x9d) were developed. These defibrillators are typically used by trained emergency medical system personnel. The major shortcoming of these defibrillators is the delay between the onset of ventricular fibrillation and the administering of a first shock. It has been estimated that survival decreases by 10% for each minute that passes after the first minute of ventricular fibrillation.
Temporary high risk patients who do not reach an ICD have little protection against sudden cardiac arrest (xe2x80x9cSDAxe2x80x9d), particularly with the discovery that anti-arrhythmia drugs have been proven to be less effective than a placebo. Accordingly, there exists a need for a defibrillator, preferably a portable, wearable defibrillator, which addresses the foregoing drawbacks of conventional defibrillators.
The present invention addresses the foregoing needs. For example, according to one aspect, the present invention is a defibrillator for delivering defibrillation energy to a patient. The defibrillator includes at least one electrode which attaches to the patient for transmitting the defibrillation energy to the patient and for receiving patient information from the patient, and a plurality of capacitors which are switchable so as to alter characteristics of the defibrillation energy. According to the invention, a controller controls switching of the plurality of capacitors in accordance with the patient information received from the at least one electrode.
By monitoring the patient for patient information and switching the plurality of capacitors in accordance with the patient information, the foregoing aspect of the invention makes it possible to deliver, to the patient, defibrillation energy which is appropriate for that patient. As a result, the invention provides increased effectiveness in the treatment of cardiac arrhythmias.
According to another aspect, the present invention is a way in which to increase long-term wear of a sensing electrode, such as a traditional defibrillation electrode (i.e., electrodes having a conductive surface area of over 60 cm2), a low-surface-area electrode (i.e., electrodes having a conductive surface area of roughly 60 to 10 cm2), or segmented electrodes (i.e., electrodes having a conductive surface area of roughly 8 to 10 cm2). Specifically, the invention includes a variety of different techniques for increasing the amount of time that an electrode can be worn by a patient without resulting in substantial skin irritation or damage. For example, according to one embodiment, one or more electrodes are moved on the patient""s body periodically. As another example, therapeutic or prophylactic agents are provided in or on the electrode. Also, the size, configuration, and materials used to construct the electrodes contribute the amount of time that the electrodes can be worn by a patient.
According to another aspect, the present invention is a defibrillator for delivering defibrillation energy to a patient. The defibrillator includes a signal generator for generating the defibrillation energy and a plurality of segmented electrodes each having a conductive area for transmitting the defibrillation energy to the patient. The plurality of segmented electrodes are divided into groups of two or more electrodes, each of the groups of electrodes having at least one line connected to the signal generator. Each of the lines has a length that is sufficient for each group of electrodes to be placed on the patient a predetermined distance away from others of the groups of electrodes. In the invention, the electrodes in at least one of the groups are spatially arranged to have an effective conductive area which is greater than a total combined conductive area of the electrodes in the group.
According to still another aspect, the invention is a segmented electrode device for use during ventricular fibrillation of a patient. The segmented electrode device includes a plurality of segmented electrodes each having a conductive area for transmitting defibrillation energy to the patient. The plurality of segmented electrodes are divided into groups of two or more electrodes, each of the groups of electrodes having at least one line connected to a signal generator. Each of the lines has a length that is sufficient for each group of electrodes to be placed on the patient a predetermined distance away from others of the groups of electrodes. In the invention, the electrodes in at least one of the groups are spatially arranged to have an effective conductive area which is greater than a total combined conductive area of the electrodes in the group.
By virtue of the electrode configurations in the foregoing two aspects of the invention, it is possible to simulate a larger conductive area using segmented electrodes. As a result, these aspects of the invention have an advantage over their conventional counterparts. That is, these aspects of the invention are able to provide defibrillation energy to the patient without using large electrodes. Thus, these aspects of the invention provide reduced skin irritation without a corresponding reduction in efficacy.
According to another aspect, the present invention is a defibrillator for delivering defibrillation energy to a patient. The defibrillator includes an external interface, over which patient information is transmitted to an external location, and a patient interface, over which the defibrillation energy is transmitted to the patient, and over which the patient information is received. A processor is included in the defibrillator, which analyzes the patient information received over the patient interface and which controls transmission of the defibrillation energy to the patient based on at least a first portion of the patient information. A memory stores at least a second portion of the patient information prior to transmission of the second portion of the patient information over the external interface.
By controlling transmission of the defibrillation energy to the patient based on at least a first portion of information received from the patient, the invention is able to tailor the defibrillation energy to the patient""s needs. Moreover, because the invention includes a memory which stores at least a second portion of the patient information, and includes an external interface over which such information may be transmitted, the invention is capable of recording patient information, such as patient electrocardiogram (hereinafter xe2x80x9cECGxe2x80x9d) information or the like for a period of time, and of transmitting that patient information to an external location, such as a central repository, hospital, doctor, etc.
According to another aspect, the present invention a defibrillator for delivering defibrillation energy to a patient. The defibrillator includes a processor and a patient interface, over which patient information is received from the patient and over which the defibrillation energy is transmitted to the patient. The processor operates in a normal mode and a low-power consumption mode, wherein, during the normal mode, the processor receives the patient information and controls transmission of the defibrillation energy in accordance with the patient information.
By having the processor operate in a low-power consumption mode, the invention reduces the amount of power consumed by the defibrillator. As a result, a power supply will last longer in the defibrillator of the present invention than in its conventional counterparts.
According to another aspect, the present invention is a defibrillation system which includes a defibrillator for delivering defibrillation energy to a patient and a base station connected to the defibrillator. The defibrillator includes a plurality of electrodes connected to the patient for transmitting defibrillation energy to the patient and for receiving patient information from the patient, and a memory which stores the patient information and defibrillation information, the defibrillation information relating to operation of the defibrillator. The defibrillator also includes a base station interface, over which the patient information and the defibrillation information are transmitted, and over which external information is received, and a controller for controlling when the defibrillation energy is transmitted to the patient based on the patient information and at least part of the external information. The base station includes a defibrillator interface which mates to the base station interface of the defibrillator and over which (i) the defibrillation information and the patient information is received from the memory of the defibrillator, and (ii) the external information is transmitted to the defibrillator. The base station also includes an external interface, over which the defibrillation information and the patient information is transmitted to an external location, and over which the external information is received from the external location.
By virtue of the foregoing arrangement, it is possible to transmit patient and defibrillation information from a defibrillator to a base station and from the base station to an external location, such as a central repository, doctor, hospital, etc. Moreover, the foregoing arrangement makes it possible to transmit external information from the base station to the defibrillator. This external information can be used, e.g., to reprogram the defibrillator, to alert a patient to a possible condition in the patient or the defibrillator, etc. In particularly preferred embodiments of the invention, a memory on the defibrillator containing patient and defibrillation information is removable, and can be transferred to the base station or to an external location for downloading.
According to another aspect, the present invention is a defibrillation system which includes a defibrillator for delivering predetermined defibrillation energy to a patient, an indicator which indicates operational defects in the defibrillator, and a base station which is interfaced to the defibrillator. The base station performs diagnostics on the defibrillator in order to detect operational defects in the defibrillator, and transmits results of the diagnostics to the defibrillator. The indicator provides an indication of such operational defects in the defibrillator when the base station detects operational defects in the defibrillator.
By alerting the patient to operational defects in the defibrillator while the defibrillator is still in the base station, this aspect of the invention is able to reduce the chances of malfunction following a cardiac arrhythmia. As a result, this aspect of the invention increases the patient""s chances of surviving an arrhythmia.
According to another aspect, the present invention is a method of treating a patient for ventricular tachycardia, bradycardia, ventricular fibrillation, or other treatable rhythm using a pacer/converter/defibrillator in accordance with the present invention (hereinafter referred to solely as a xe2x80x9cdefibrillatorxe2x80x9d). The method includes monitoring the patient for a predetermined condition via one or more electrodes on the defibrillator, sending a message to the patient in response to the predetermined condition, activating the defibrillator so that the defibrillator delivers defibrillation energy to the patient, and storing at least one of the results of the monitoring, sending and activating steps in a memory on the defibrillator. The method also includes downloading information stored in the memory of the defibrillator to a base station having an external interface, and transmitting the information downloaded from the memory of the base station to an external location via the external interface of the base station.
By sending a message to the patient in response to the predetermined condition, by processing the patient""s response, and by other consciousness detection methods, the present invention is able to reduce the chances of defibrillation energy being delivered to the patient while the patient is still conscious. Moreover, the foregoing aspect of the invention is able to store at least some information relating to the arrhythmia and the patient""s response thereto, and to download that information to a base station, from whence the information may be transmitted to an external location for analysis or the like.
In this regard, according to another aspect, the present invention is a base station for use with a defibrillator. The base station includes a defibrillator interface over which information is exchanged with the defibrillator, an external interface over which information is exchanged with an external entity, and a controller. The controller (i) receives patient information and defibrillation information from the defibrillator, (ii) transmits the patient information and defibrillation information to the external entity, (iii) receives defibrillator programming information from the external entity, (iv) programs the defibrillator in accordance with the defibrillator programming information, (v) performs diagnostics on the defibrillator, and (vi) transmits results of the diagnostics to at least one of the defibrillator and the external entity.
Thus, the base station of the present invention may both act as an interface between a defibrillator and an external entity and provide a patient with a means to ensure proper operation of the defibrillator.
According to another aspect, the present invention is a method for reprogramming a defibrillator based on a central database of information relating to patients that use a type of defibrillator. The method includes collecting, in the central database, information relating to a plurality of patients that use the type of defibrillator, analyzing the information stored in the central database so as to test an algorithm for detecting irregular heart activity, and correcting the algorithm for detecting irregular heart activity based on a result of the analyzing process. The method also includes transmitting a corrected algorithm to a plurality of base stations corresponding to the plurality of patients, and reprogramming a defibrillator in each of the base stations using the corrected algorithm.
By providing a way in which to test algorithms for detecting irregular heart activity, a way in which to correct such algorithms, and a way in which to reprogram a defibrillator with a corrected algorithm, the present invention is able to improve its performance over time.
In preferred embodiments, the invention features a long-term cardiac monitoring and defibrillation system that is wearable by a patient. The system includes at least two electrode arrays electrically connected to a portable defibrillator. The electrode arrays are spatially separated and adhered to portions of the patient""s skin in the thoracic window area for an extended period of time, such that electrical activity of the heart can be monitored and effective defibrillation and/or pacing impulses can be delivered to the patient""s heart. The electrode arrays comprise plural electrodes which are capable of sensing the patient""s heart condition by detecting the electrical activity of the heart, and of delivering defibrillation or pacing impulses to the patient""s heart when required.
In another aspect, the cardiac monitoring and defibrillation system of the invention comprises features which enhances the long-term wearability of the system. These features include use of a low-current defibrillation waveform and electrodes having a composition and/or geometric design adapted to minimize the area of the electrodes. In this regard, it has been determined that use of a lower current than that typically used for defibrillation can provided effective defibrillation, particularly when coupled with electrode arrays having electrode surface areas which are significantly smaller than the surface area of conventional defibrillation electrodes. The use of reduced area electrodes minimizes irritation to the skin. These features also permit higher impedance materials to be used in the electrodes, which is also less irritating to the patient""s skin.
In one aspect, the electrode array comprises multiple spatially separated electrodes separated by non-conductive material, passive material or free space. The use of multiple smaller electrodes minimizes the electrode area in contact with the skin needed to deliver an effective defibrillation impulse to the heart, thereby reducing the area of skin in contact with electrode materials.
Another aspect of the invention features a long term cardiac monitoring and defibrillation system and method that ameliorates, reduces or prevents irritation of the patient""s skin caused by delivery of defibrillation impulses and/or by the constant contact of the electrodes with the skin. According to this aspect skin that becomes irritated from contact with the electrodes is permitted to recover by periodically detaching the electrode arrays and moving or rotating them by a predetermined amount, and re-affixing either the same or new electrode arrays to different portions of the skin within the patient""s thoracic window area. This moving or rotating allows substantially different sections of the patient""s skin to be in contact with the electrodes so that portions of the skin previously in contact with the electrodes are allowed to recover.
The electrode arrays of the present invention preferably are designed for long term patient wearability. To this end, the electrode arrays include a therapeutic or prophylactic material which ameliorates, reduces or prevents irritation to the patient""s skin in contact with the electrode arrays. Therapeutic or prophylactic materials may include, for example, wound healing agents, moisturizers, emollients, protective agents or antibacterial agents. Each electrode array comprises electrically conductive areas (electrodes) and electrically non-conductive areas (passive areas). The electrodes are capable of sensing the electrical activity of the heart, delivering electrical impulses (cardio and defibrillation) to the heart, as well as tactile stimulation and pacing signals.
The electrode arrays preferably include an adhesive portion for adhering the array directly to the skin. However, external means for retaining the electrode arrays in electrical proximity to the skin may be used, such as a vest or a band. Long term wearability of the electrode arrays may be enhanced by selecting materials for use in the electrode array which minimize irritation to the skin in contact with the array. Such materials may include, for example, adhesives and backing materials having a high moisture vapor transmission rate and conductive materials for use in the electrodes having low salt (ionic) concentrations or comprised of silicone or other adhesive materials that are conductive by means of additives.
In another embodiment, long term wear can be enhanced and skin irritation reduced by including in the system means for monitoring, and adjusting as necessary, the environment at the interface between the electrode array and the skin. Such means may include, for example, means for monitoring and adjusting the {PH at the skin-electrode interface in order to maintain a neutral non-irritating interface; and means for controlling the ion flow at the interface between the electrodes and the skin. In the latter embodiment, ion flow would be reduced to a minimum except for the short time during which a defibrillating shock is being delivered, at which time the ion flow would temporarily increase to provide a conductive path for the defibrillation impulse.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiments thereof in connection with the attached drawings.